The present invention relates generally to cement pumps, and more specifically to double acting cement pumps employing a pair of power driven, oppositely reciprocating pistons sliding in a pair of cylinders for the pumping action.
Reciprocating cement or concrete pumps are described in my U.S. Pat. Nos. 4,174,928 and 4,634,352. In U.S. Pat. No. 4,634,352, a cement pump of this type is described in which each cylinder outlet is connected to a respective pump response chamber having a valve controlled inlet for connection to a supply of cement or the like. The pump chamber outlets are each connected to a discharge chamber for controlling their connection to a delivery outlet, and a ball valve in the discharge chamber moves between the discharge chamber inlets to alternately isolate the flow of material from the two pump chambers in response to the pumping action.
The cement pump in my previous patents referred to above was of generally unitary construction. It is not easy to clear any clogged material from such an arrangement, and the ball valve seats in the discharge chamber will become worn relatively quickly, resulting in insufficient isolation of the pump chambers and inefficient pumping operation. Thus the entire pump must be replaced fairly often. Also, different jobs may require the use of pre-mixes having different water content, and therefore different viscosity. U.S. Pat. No. 4,634,352 described a pump in which the inlet valves could be readily adjusted for different viscosity materials. However, no adjustment of discharge or outlet valve was provided in this pump.